Engine oil is the lifeblood of the turbine engine and proper turbine engine oil system function is vital for engine performance. The turbine engine oil system functions to lubricate and cool the engine bearings, gears, and seals and provides hydraulic power for some auxiliary systems. Maintaining the turbine engine oil system pressure and oil temperature within normal operating limits ensures proper turbine engine oil system function. Oil temperature is generally determined by engine heat rejection (i.e., the amount of heat that the engine puts into the engine oil), generator heat rejection (i.e., the amount of heat that the engine generator puts into the engine oil), and oil cooler system performance. Higher than normal oil temperatures may be caused by, for example, low oil, insufficient or ineffective oil cooling (from, for example, oil cooler clogging), blocked oil lines, and/or the engine may be producing too much heat. Certain aircraft and engine operating conditions, environmental conditions, and unique engine characteristics impact oil temperature. Oil temperature is typically highest at high altitudes, high ambient temperatures, and high loads. Increased levels of air pollution and increased frequency of aircraft taking off from and landing at airports located at higher base level altitudes (at about 15,000 feet) have increased the extent of engines operating at higher than normal oil temperatures.
With conventional aircraft oil systems, a high oil temperature (hereinafter “HOT”) fault warning is annunciated in some manner (e.g., fault light, screen, code, etc.) when the engine oil temperature exceeds a single predetermined HOT fault limit that is higher than normal operating temperatures. The single predetermined HOT fault limit is typically provided in the Model Specifications for a particular engine. The single predetermined HOT fault limit is inexact, without taking into consideration actual aircraft and engine operating conditions, environmental conditions, and unique engine characteristics. While a HOT fault warning can be alarming and, in the worst case scenario, may result in an aborted flight, the condition is usually momentary. However, by the time of the HOT fault warning, the engine may have already incurred undesirable wear as a result of engine operation at higher than normal oil temperatures. For example, engine operation at higher than normal oil temperatures may accelerate the accumulation of carbon particles in the engine oil (hereinafter referred to as “oil coking”) and the deterioration of oil additives. Increased oil coking may lead to increased seal wear and adversely impacts gear and bearing life. Increased oil coking can also result in removal of the engine from service and can increase engine overhaul costs.
Attempts have been made to monitor engine oil temperatures as part of overall engine condition trend monitoring using computer software. Recorded trend data may be sent to a designated analysis center on the ground for processing and recommendations. Trend monitoring requires investment in developing and purchasing expensive equipment and performing complex statistical analyses based on historical data for assessing overall engine health.
Accordingly, it is desirable to provide methods and systems for monitoring engine oil temperatures of an operating engine. It is also desirable to provide simple and relatively inexpensive monitoring methods and systems to detect higher than normal oil temperatures and provide an early maintenance-required oil temperature (MROT) warning before substantial engine wear has occurred and before the oil temperature reaches the single predetermined HOT fault limit value, thereby resulting in reduced maintenance, overhaul requirements, and engine removals. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.